Analysis of the Unsteady Loads on Train Models in Wind Tunnels

Wind tunnel tests were performed to measure the loads on a train model under disturbed incoming flow conditions. For this purpose, a wing system with movable flaps was used to generate harmonic fluctuations in the flow upstream of the train model. The model was mounted above a moving belt to generate a more realistic underbody flow and the loads were measured using an internal balance. The tests show that the mean drag and the lateral force response can be analyzed although vibrations in the setup influence the measured force signals. Evidence was found that the drag coefficient increases when incoming flow disturbances are present. Phase-averaging was used to filter out the part of the lateral force fluctuation related to the incoming flow disturbance. The resulting lateral force response depends strongly on the frequency of the incoming flow disturbances.